Hello I just got my puppy 5 days ago, he just turned 7 weeks old on tuesday and he only weighs 8.2lbs! Why is my puppy so little? he is Purebred GSD AKC registered and everything, but according to all the GSD charts he should weigh between 15 and 20lbs by the end of next week and there is no way he will gain that much weight in 6 days. I feet him 3/4 a cup twice a day of the Purina Pro Plan large breed puppy food. Should I be feeding him more food?